/Engine/Source/Runtime/InteractiveToolsFramework/Public/BaseGizmos/CombinedTransformGizmo.h
If used, binds alignment functions to the sub gizmos that they can use to align to geometry in the scene. Specifically, translation and rotation gizmos will checkShouldAlignDestination()to see if they should use the custom ray caster (this allows the behavior to respond to modifier key presses, for instance), and then useDestinationAlignmentRayCaster()to find a point to align to. Subgizmos align to the point in different ways, usually by projecting onto the axis or plane that they operate in.
virtual void SetWorldAlignmentFunctions ( [TUniqueFunction](API\Runtime\Core\Templates\TUniqueFunction)< bool()> && ShouldAlignDestination, [TUniqueFunction](API\Runtime\Core\Templates\TUniqueFunction)< bool(const FRay &, FVector &)> && DestinationAlignmentRayCaster )